1. Field of the Invention
The invention relates to a head mounted display system for producing a replica of an image for viewing by an observer. More specifically, the invention relates to such a system which uses a projection screen as part of an image transmission arrangement in order to obtain a non-pupil forming display.
2. Description of Prior Art
Virtual Reality and Remote Presence are closely related fields in which various devices are used to create an impression in the mind of the subject that he or she is in a different and separate environment from actual reality. The term "Virtual Reality" is usually confined to the use of completely artificial environments, usually created by computer graphic systems. Visual simulation devices used for training pilots etc., are an example of "Virtual Reality". The term "Remote Presence" is usually used in situations where an observer controls the position of one or more television cameras placed at some distance from the observer, and views the resulting image in such a way as to obtain the feeling that he or she is situated in the same position occupied by the cameras.
It is advantageous for both types of systems to use a head mounted display and to control the displayed image by means of the observers head position. The present invention is a particularly advantageous type of just such a display.
Previous systems have used small television displays of various types either mounted on or attached to the head in some way. The observer views the display through an eyepiece to obtain a magnified virtual image. The disadvantage of all these devices is the low resolution, absence of colour or small field of view inherent in their design. The present invention overcomes these shortcomings by using a fiber optic cable to relay an image from a high resolution television projector to the observer's head where it is viewed through wide angle eyepieces.
Helmet displays using fiber optic cables to carry the image from an off-helmet display device to the helmet are known in the prior art as illustrated in, for example, U.S. Pat. No. 4,348,185, Breglia et al, Sep. 7, 1982, U.S. Pat. No. 4,439,157, Breglia et al, Mar. 27, 1984, U.S. Pat. No. 4,439,755 LaRussa, Mar. 27, 1984 and U.S. Pat. No. 4,743,200, Welch et al, May 10, 1988.
In the '185 patent, a visual scene is transmitted by CRT's 37 and 39 through fiber optic cables 51 and 53 respectively. The scene is then transmitted through an optic system including lenses 57 and 59 and beam splitter 61, onto a reflective screen 63. The scene is then reflected from the screen 63 to the eyes of an observer and the data from two optical paths overlap whereby the scene is seen by the observer to appear at optical infinity.
In the '157 patent, computer generated optical images are transmitted through fiber optic cables 20 through a helmet mounted optical system 10 and onto a domed screen (not shown in the drawings).
In the '755 patent, an optical path coupler 14 is secured to a helmet 22 of an observer so that its angular orientation is a function of the head movement of the observer. A display is provided of meter-type data and/or topographical features in the ordinary line of site of the observer.
In the '200 patent, an optical image is fed, via a fiber optic cable, to an eyepiece of an observer. The eyepiece is preferably a wide angle eyepiece mounted on the helmet of the observer. A replica of the image is produced in the line of site of the observer, the replica appearing to originate at a distance.
The '755 patent, the '200 patent, and the '185 patent all include within their teachings means for tracking the head movements of the observer, and the '157 patent includes within its teachings means for tracking the eyes of the observer.
The above-described systems are not suitable for general use due to their size, cost and complexity.